1. Field of the Invention
This invention relates generally to orthodontic appliances, and is more particularly concerning with a resiliently expandable arrangement that normally applies a force between the upper and lower teeth but is sufficiently extendible to allow free movement of the mandible.
2. Discussion of the Prior Art
It is common in orthodontics to utilize appliances that exert a force between the maxillary and the mandibular dentitions in order to induce orthopedic and/or orthodontic correction. Early forms of such appliances comprise simply coil springs connected between the maxilla and the mandible. While these springs will exert the force needed, they are uncomfortable for the patients in that the cheek Gets pinched in the coils of the spring, and food and the like accumulates in the springs. Additionally, they have been of very short life because of rapid and frequent breakage while severely restricting the movement of the mandible.
One solution to the above mentioned problems is to cover the springs as shown in the patent to Armstrong, U.S. Pat. No. 3,618,214. While such a covering diminishes the problems, it does not affect the problem of limited mandibular motion. More recent efforts at solving the problems are shown in patents U.S. Pat. No. 4,708,646 to Jasper and U.S. Pat. No. 4,795,342, to Jones. The Jones device has a spring enclosed within a cylinder, but still allows very limited motion. The Jasper device has a spring encased in an elastic material, and provides somewhat loose connections to give some freedom, but still does not allow full motion of the mandible.